(1) Summary of the Invention
The present invention relates to a method for inhibiting Listeria monocytogenes, a foodborne pathogen, in a food or other materials which can be contaminated by this pathogen using a bacteriocin. In particular the present invention relates to the use of a bacteriocin derived from Pediococcus acidilactici to inhibit the Listeria monocytogenes in the food or other materials which can be contaminated by this pathogen.
(2) Prior Art
The term "bacteriocin" refers to a protein of the colicin type, characterized by lethal biosynthesis by the producing bacterium, intraspecific activity in related species of bacteria, and adsorption to specific receptors on the sensitive bacteria (Tagg, J. R., A. S. Dajani, and L. W. Wannamaker, Bacteriol. Rev. 40:722-756 (1976)). Bacteriocins have been described as being produced by many bacteria, however the bacterial strains inhibited by the bacteriocin are usually related to the strain which produces the bacteriocin (Gonzalez, C. F., and B. S. Kunka, Appl. Environ. Microbiol. 53:2534-2538 (1987)).
In U.S. Pat. No. 4,883,673, filed Feb. 9, 1987 by Carlos Gonzalez, which is assigned to a common assignee, the preparation and use of a bacteriocin derived from Pediococcus acidilactici, particularly Pediococcus acidilactici NRRL-B-18050, to inhibit spoilage bacteria, particularly Lactobacillus fermentum and Lactobacillus bifermentum, is described. These spoilage bacteria are lactic acid producing strains of the genus Lactobacillus and Pediococcus. No activity was found against Lactococcus lactis, Lactococcus lactis subsp. diacetylactis, Lactococcus cremoris (previously in the genus "Streptococcus") or Streptococcus thermophilus, Staphylococcus aureus, Micrococcus varians, Micrococcus sodonensis, Staphylococcus xylosus, Staphylococcus epidermidis, Staphylococcus carnosus, Lactobacillus acidophilus, Lactobacillus lactis and Lactobacillus bulgaricus. It was concluded that the bacteriocin had a limited range of inhibitory activity related to gram positive, lactic acid bacteria.
Listeria monocytogenes has been demonstrated to be transmitted in contaminated food. (J. Applied Bact. 63:1-11 (1987)). While the culture is sensitive to pH and an acid environment will usually inhibit the growth of this microorganism, there are many instances of foods where the pH is not sufficiently acidic.
Listeria monocytogenes produces severe illness in animals and humans. The characteristics of the disease and this species are described in J. Applied Bact. 63:1-11 (1987). Listeria monocytogenes grows well at refrigeration temperatures and thus usual means of inhibiting the growth of Listeria monocytogenes by refrigeration is ineffective. Because of this there are problems in the marketplace, an example of which is the recently published recall of several brands of Listeria contaminated ice cream bars. Accoding to Bergey's Manual of Systematic Bacteriology, Vol 2: 1235-1245, (1986), the taxonomic position of the genus Listeria with regard to other genera is still not resolved. However, it is clear that Listeria monocytogenes is quite distinct from Lactobacillus, Staphylococcus, Micrococcus, Pediococcus and Streptococcus (Lactococcus).